The invention relates to security tape for mounting on a plastic information bearing substrate, a document or other element.
Credit cards are considered by most people in the United States to be an essential of modern life. Typically, information is printed and embossed on a plastic substrate identifying the holder of card and the issuer. A magnetic strip contains similar information and is mounted on one side, normally the rear side, for storing the information magnetically. Inevitably, increased counterfeiting of such cards has accompanied the increase in their use. This has in turn lead to great interest in incorporating into each individual card measures making counterfeiting as difficult as possible.
One technique now being adopted is to provide on each credit card a small difraction grating forming an image which appears to be three dimensional at least in the horizontal direction. Such a difraction grating is more commonly known as a hologram and is manufactured by interferring coherent laser light reflected from or transmitted through an object with light transmitted directly from the laser and serving as a reference. Such a hologram when reconstructed with coherent light from the same or a similar laser provides an image which appears to have three dimensions, i.e. appears to have depth. Of course, lasers are not normally available at locations such as restaurants and shops where credit cards must be inspected. However, through the use of conventional techniques a difraction grating of this sort can be made which is viewable in natural light, i.e. a so called white light viewable hologram.
Credit cards are now being issued incorporating such a white light viewable hologram on the front surface of the card. Such a hologram is relatively difficult to manufacture and requires fairly complex equipment. Therefore, the average counterfeiter is discouraged if not entirely prevented from attempting to counterfeit such a card. Moreover, the authenticity of the white light viewable hologram and hence the card can be readily ascertained by any unskilled person even under poor light simply by viewing the hologram and observing whether it has the illusion of depth and changing colors which are the characteristics of a white light viewable hologram. While providing satisfactory protection or at least discouragement of counterfeiting this arrangement has several drawbacks.
First, the space available on the front of the card is very limited. Most issuers of such cards want to use all of the space for imparting that commercial information and for identifying themselves and the issuer of the card. If the hologram is made too small it may be difficult for the clerk or other person accepting the card to see whether the hologram is truly there and whether it is simulated. Discarded cards, even if cut in two, may still have a full hologram which can be transferred to a counterfeit card for fraudulent use.
According to the present invention, an optically viewable hologram is formed on the magnetic strip which is normally mounted on the rear of the card for storing information about the card magnetically. This reserves the entirety of the front of the card for use by the issuer for whatever purpose he may desire. The hologram on the magnetic strip is relatively large in area and is very easy to identify as such. In addition, placing the hologram on the rear of the magnetic strip encourages the clerk or other person accepting the card to turn over the card and check the signature panel. This is rarely done at the present time.
According to the method of the present invention, a white light viewable hologram is first cast, for example as taught in application Ser. No. 505,888 filed June 20, 1983. More specifically, a hologram is formed on one side of a carrier of clear plastic. The hologram may be embossed on a metallized carrier or cast on clear plastic and made visible by deposit of a non-magnetic metal or application of a non-magnetic ink. The hologram is then coated with ferrous oxide to form a magnetic strip with an optically viewable image thereon. The magnetic strip can then be mounted onto a plastic substrate and the carrier removed to form the card of the present invention. If desired miniscule clear glass beads or other light scattering compounds can be provided between the layer of clear material and the ferrous oxide to provide the possibility of yet another authentication of the card as well as making the holographic image more impervious to counterfeiting through reconstruction by laser techniques.
Other objects and purposes of the invention will be clear from the following detailed description of the drawings.